It is known to impart fire-resistance to cellulosic substrates by impregnation with certain agents. See, for example, U.S. Pat. No. 2,870,042 (textiles); U.S. Pat. No. 3,027,295 (paper); U.S. Pat. No. 3,242,004 (wood). In general, the fireproofing agents fall into two classes: (1) non-permanent materials that are susceptible to leaching, e.g. the phosphates, borates and sulfonates, and (2) permanent materials that are leachproof, e.g. tris(1-aziridinyl)phosphine oxide and melamine resins. It is, of course, more desirable to have permanent protection but the permanent materials have several processing difficulties that render commercial fireproofing impractical. E.g. toxicity, long curing times, high temperature curing and multiple stage processes requiring expensive equipment.
One step in solving the above problems was described in U.S. Pat. No. 3,565,679 in which cellulosic substrates were rendered fire-resistant by treatment with an aqueous solution of a complex of a polyalkylenepolyamine and a condensation product of phosphorus pentoxide and ammonia.